1. Field of the Invention
This invention relates generally to a means for continuously feeding material such as yarn into a vacuum system while preserving the vacuum. More particularly, the invention relates to a sealing means for a gaseous-plasma vacuum system wherein the sealing means includes upper and lower metal blocks. An open bottom air chamber in the lower surface of the upper block, and a longitudinal groove in the upper surface of the lower block are separated by a flexible membrane. When air under pressure is supplied to the air chamber in the upper block the flexible membrane is forced downwardly against the groove in the lower block and the material moving therethrough, causing the material to conform to the shape of the groove, thus effecting a seal.
2. Description of the Prior Art
Inflatable seals have been used in the past. Such seals are conventionally located in a groove in one of a pair of confronting surfaces and inflation of the seal is arranged to cause an upper portion of the seal to deform into sealing contact with the other surface. Such a seal is disclosed by U.S. Pat. No. 3,788,651.
Pressure operated flexible membranes have also been used in the past to control the movement of material from one region to another where the regions are at different pressures. U.S. Pat. No. 2,470,744, for example, relates to a two-stage pneumatic valve arrangement for the transporting of particles, batchwise, between regions at substantially different pressures. The device comprises essentially a conduit having a pair of valves arranged in tandem therein, positioned at longitudinally-spaced regions. Upon operation of the valves, sealing is accomplished by means of air pressure on a pair of flexible membranes, forcing them against valve seats positioned in the center of the conduit.
U.S. Pat. No. 2,598,207 relates to valving means for shutting off or regulating the flow of pulverized or granular materials or fluids generally through a confining conduit. The apparatus comprises an expansible bag positioned within a conduit. The bag may be fastened to the inner wall of the conduit or in an interior depression therein and may be inflated or deflated to control the flow of material therethrough. The bag may extend throughout substantially the entire length of the conduit or only a portion thereof. Means responsive to variations in pressure in the conduit are provided to result in corresponding variations in control of the pressure within the inflatable member.
U.S. Pat. No. 2,604,246 relates to a feeding apparatus which comprises a valve which is particularly adapted for use in controlling the flow of finely divided, free-flowing materials. The valve in general comprises a rigid outer wall or casing, within which is inserted a thin elastic lining, which is normally positioned adjacent the rigid outer wall, but which may be laterally distended or stretched as by air pressure to a position in which its inner surfaces contact each other over a substantial area, thereby closing off the passageway normally existing centrally thereof. Air pressure is exerted against the outer surfaces of the inner lining, and is applied in such a way as to cause the central portion of the elastic walls to contact first, after which the walls contact progressively downward. The lower half of the walls of the inner lining is made thinner than the upper half as a further aid in causing the bottom portion of the lining to move downwardly upon application of air pressure, thereby exerting a pushing action on any material present centrally of the two but nearer the bottom thereof.
In the past, one of the main problems in the treatment of fibers with plasma on a commercial scale was the need for a means of introducing the material continuously via seals into an environment maintained at a lower-than-ambient pressure while still preserving the vacuum. The foregoing disclosures offer no solution to this problem.